Problem: The measures of the three interior angles of a triangle are $50^\circ$, $55^\circ$ and $x^\circ$. What is the degree measure of the largest interior angle of this triangle?
Solution: We know that the interior angles of a triangle sum to $180^\circ$, so $50^\circ + 55^\circ + x^\circ = 180^\circ$. It follows that $x = 75$. Thus, this triangle has angles of $50^\circ$, $55^\circ$, and $75^\circ$. The largest of these three angles is $\boxed{75^\circ}$.